Decibel question

You can get a calibrated microphone for "normal" phones from Parts Express. The imm6 I think it is called. 

Second, how high you can turn up the volume is a matter of speaker efficiency, impedance and amplifier "size" or power output at that impedance. A speaker swap could make your ears bleed. :) 

Best,

E

Am I missing something not being able to listen to 100 plus?

Only you can answer that question. But as you've stated at one point your ears were hurting, regardless of whatever you may be missing, your first priority (IMO) becomes protecting your ears from permanent damage. There are plenty of ear plugs available if your desire is to attend concerts and you're finding the SPL to high. 

You may be interested in reading a related and recent thread here on Audiogon.  https://forum.audiogon.com/discussions/does-it-have-to-be-loud

Am I missing something not being able to listen to 100 plus?

Hearing damage, maybe?

FWIW - I use a Radio Shack Sound Level Meter.
Set to C weighting and Slow response for a display of "average" dB levels at a given volume setting, 75 - 85 is typical at the listening position (around 10-12 feet from speakers). Loud but still comfortable for me is pushing the average to a more consistent 80-85 (same meter settings). At these levels, using Fast response for peaks, I see "typical" peak values of 90-95...and definitely still less than 100 dB.   What's very satisfactory for me might not be for you.  Can't speak to that (or whether your amp/speaker match is ideal).

Hope this gives you additional context.

The iPhone case may cover the microphone, lowering the actual SPL so I wouldn't trust that for accuracy.

All too often, the sound you hear at a rock concert can be heavily distorted, especially when it is loud.    In many instances, that distortion is deliberately induced, because people think it sounds "cool".    The distortion may arise from the acoustics of the space in question, it can by caused by the electric instruments being used, and it can also occur if the sound technicians at the concert overdrive their amplifiers. Distorted sound at 90db can be excruciating. 

By contrast, when you listen to a well-produced recording at home on a great stereo, the relative amount of distortion in the music you hear will be low.    In fact, if you don't over-drive your amplifiers, (and allowing for the acoustics of your room), the only distortion you should hear should be that from the program material to which you listen (CD/record/tape).    Under those circumstances, you should find that your stereo still sounds great even when I play it at high decibel levels.